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To investigate the variability of a Pseudomonas savastanoi pv. savastanoi population, 53 isolates of the bacterium, isolated in Albania, Italy, Morocco, Portugal and Turkey from knots of several olive cultivars, were characterized at molecular levels by rep-PCR and f-AFLP. All bacterial strains were pathogenic on olive plants and produced fluorescent pigments on King’s B medium. They were negative for levan, oxidase, arginine dihydrolase and potato soft rot and induced hypersensitive reaction in tobacco plants. Based on these results and on the amplicon generation of the iaaL and the ptz genes by PCR, all the isolates can be considered belonging to P. savastanoi pv. savastanoi. Rep-PCR analysis, performed using ERIC primers and the novel primers KRP2-KRP8 and KRPN2, demonstrated that fingerprints obtained with the novel primers were more polymorphic with respect to those generated with ERIC primers. UPMGA, performed combining data from the 3 primer sets, revealed 26 distinct fingerprints with an overall similarity of about 82%. Most of the isolates from Morocco and Umbria (Italy) as well as the pathovar reference strain of P. savastanoi pv. savastanoi are grouped in a cluster. In addition, all Turkish and Albanian isolates and most of the isolates from Apulia (Italy) form another cluster. F-AFLP analysis provided a significantly higher resolution than the rep-PCR and revealed high polymorphisms between the isolates. It has the potential to play a major role in characterizing P. savastanoi pv. savastanoi populations. Virulence tests were performed on the olive cv. Frantoio with 19 bacterial isolates, selected on the basis of rep-PCR fingerprints. Wide virulence variability among the isolates was found. Knot volume significantly correlates with knot weight, allowing the evaluation of disease 1 Dipartimento di Scienze Agrarie e Ambientali, Universita degli Studi di Perugia, via Borgo XX Giugno 74 06121 Perugia, Italy 2 MAIB-CIHEAM The Mediterranean Agronomic Institute of Bari, via Ceglie 9 – 70010 Valenzano (Bari), Italy 3 Institut Agronomique et Veterinaire Hassan II, Complexe Horticole d’Agadir, BP. 18/S, Agadir, Morocco Author correspondence: C. Moretti; e-mail: chiaraluce.moretti@unipg.it M’B. Fatmi et al. (eds.), Pseudomonas syringae Pathovars and Related Pathogens. 321 © Springer Science + Business Media B.V. 2008 322 C. Moretti et al. progress in a non-destructive manner. Sequencing of genetic traits of the bacterium likely involved in its pathogenicity and virulence is in progress. |
